It could also be possible that the browser might not recognize the version of jdk you are using to compile the file. Try this, compile the applet for a lower rated version. You can do this in the following manner. In the shell or Dos prompt, compile the applet by entering -

javac YourClassName.java -target 1.1

This creates the class according to JDK 1.1 specifications. It helped me solve a problem once, all the best to you.